X-15 Flight 91

Flight 91
Mission type	Test flight
Operator	US Air Force/NASA
Mission duration	11 minutes, 8.6 seconds
Distance travelled	543.4 kilometers (337.7 mi)
Apogee	107.96 kilometers (67.08 mi)
Spacecraft properties
Spacecraft	X-15
Manufacturer	North American
Launch mass	15,195 kilograms (33,499 lb)
Landing mass	6,260 kilograms (13,800 lb)
Dry mass	6,577 kilograms (14,500 lb)
Crew
Crew size	1
Members	Joseph A. Walker
Start of mission
Launch date	August 22, 1963, 18:05:57 UTC
Launch site	NB-52A #52-003, Edwards; Dropped over Smith Ranch Dry Lake; 39°20′N 117°29′W / 39.333°N 117.483°W
End of mission
Landing date	August 22, 1963, 18:17:05 UTC
Landing site	Rogers Dry Lake, Edwards
	; Joe Walker

X-15 Flight 91 was an August 22, 1963 American crewed sub-orbital spaceflight, and the second and final flight in the program to fly above the Kármán line, which was previously achieved during Flight 90 a month earlier by the same pilot, Joseph A. Walker. It was the highest flight of the X-15 program.

Flight 91 was the first internationally recognized spaceflight of a reused spacecraft, as Walker had also flown plane number three on the previous sub-orbital spaceflight over the Kármán line on July 19. The flight was air-launched from a modified Boeing B-52 Stratofortress support plane over Smith Ranch Dry Lake, Nevada, United States. Walker piloted the X-15 to an altitude of 107.96 km and remained weightless for approximately five minutes. The altitude was the highest crewed flight by a spaceplane to that time, and remained the record until the 1981 flight of Space Shuttle Columbia.

Walker landed the X-15 about 12 minutes after it was launched, at Rogers Dry Lake, Edwards Airforce Base, in California. This was Walker's final X-15 flight.